Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents are used not only for mechanical intervention but also as vehicles for providing biological therapy. To effect a controlled delivery of an active agent in stent medication, the stent can be coated with a biocompatible polymeric coating. The biocompatible polymeric coating can function either as a permeable layer or a carrier to allow a controlled delivery of the agent.
Although stents work well mechanically, the chronic issues of restenosis and, to a lesser extent, stent thrombosis remain. Pharmacological therapy in the form of a drug delivery stent appears to be a feasible means to tackle these issues. Polymeric coatings placed onto the stent serve to act both as the drug reservoir and to control the release of the drug. One of the commercially available polymer coated products is stents manufactured by Boston Scientific. For example, U.S. Pat. Nos. 5,869,127; 6,099,563; 6,179,817; and 6,197,051, assigned to Boston Scientific Corporation, describe various compositions for coating medical devices. These compositions provide to stents described therein an enhanced biocompatibility and may optionally include a bioactive agent. U.S. Pat. No. 6,231,590 to Scimed Life Systems, Inc., describes a coating composition, which includes a bioactive agent, a collagenous material, or a collagenous coating optionally containing or coated with other bioactive agents.
Subacute thrombosis and neointimal hyperplasia are considered to be the leading complications after stenting. Various factors are believed to be involved in the process. Methods for reducing thrombosis and restenosis have been previously proposed. However, those methods are less satisfactory for reducing late thrombosis and/or restenosis associated with stenting.
Therefore, there is a need for a coating on a stent that provides for reduction of early and late thrombosis and/or restenosis.
The embodiments disclosed herein address the above described problems.